An accidental explosion ripped through an armoury in central China and killed 17 soldiers while they were stacking ammunition, state media has said.

The blast took place on Tuesday afternoon in the Hunan province city of Hengyang and its cause was under investigation, the official Xinhua News Agency said.

A Hengyang city policewoman surnamed Xiao confirmed the accident on Wednesday and said no civilians were injured. The armoury is in a rural township on the outskirts of Hengyang.

China's military operates with a high degree of secrecy and information about explosions, plane crashes and other accidents is usually tightly controlled.

With 2.3 million members, China's military is the world's largest. There have been upgrades to equipment and living conditions for soldiers fuelled by two decades of soaring defence spending but conditions for troops remain basic and oversight is often lax.